consulate in benghazi. four americans were killed as you know in tuesday's attack including the u.s. ambassador to libya chris stevens. investigators say if the violence was carried out by a specific group or if it was planned they can't say yet, that's why they are investigating. according to reports out oof libya, four people have already been arrested for these attacks. meanwhile, it was a heart breaking tribute for those four americans who lost their lives in the libyan attacks. >> we welcome home for the final time ambassador chris stevens. mr. sean smith, mr. glen doherty and mr. tyrone woods. >> president obama took part in the transfer of remains ceremony at andrews air force base yesterday along with vice president biden and secretary of state hillary clinton. he spoke of the ultimate sacrifice made for our country. >> they had a mission. and they believed in it. they knew the danger and they accepted it. they didn't simply embrace the american ideal. they lived it. >> the president also vowed to b